Article (website)  (2005)  Page(s) 6.  
 
"Elze's third cultivar was 'Perle von Zerbst', a delicate flesh-coloured Bourbon from 1872."

Book  (1936)  Page(s) 767.  
 
Zerbst, Perle von (bourbon) Elie [sic] 1872; tender flesh-white

Book  (1880)  Page(s) ??.  
 
Perle Von Zerbst, Bourbon, Elze, 1872